The present invention relates to a semiconductor device in which a semiconductor chip generating heat is located between a pair of heat sinks and to a method for manufacturing the device.
A semiconductor chip such as a power IC, which controls a large amount of electric power and current, generates so much heat that a semiconductor device using the chip requires a heat sink to dissipate heat. As shown in FIG. 7, in a proposed semiconductor device 1, a semiconductor chip 4 and a heat sink coupler 5 are located between a pair of heat sinks 2, 3. One heat sink 2 and the chip 4 are soldered together, the chip 4 and the coupler 5 are soldered together, and the coupler 5 and the other heat sink 3 are soldered together. A mold resin 7 covers the chip 4, the heat sink coupler 5, and the heat sinks 2, 3 such that the heat sinks 2, 3 are exposed from the surface of the resin 7. Because the resin 7 covers neither of the outer surfaces of the heat sinks 2, 3, heat is efficiently transferred from the heat sinks 2, 3 from both sides of the chip 4.
The semiconductor device 1 is molded in a mold 8 that includes a lower mold 8a, an upper mold 8b, and a movable mold 8c, as shown FIG. 7. The movable mold 8c presses the device 1 during the molding to prevent the resin 7 from covering the outer surfaces of the heat sinks 2, 3 while adjusting the pressure applied to the device 1 during molding. Therefore, the structure of the mold 8 is relatively complicated and the production cost of the mold 8 is relatively high. Thus, the production cost of the semiconductor device 1 is relatively high. Although the pressure applied to the device 1 is controlled, the semiconductor chip 4 tends to break during the molding because there is nothing to limit the force the chip 4 receives from the mold 8.
In addition, the outer surfaces of the heat sinks 2, 3 need to be insulated when the completed device 1 is inspected, screened, or assembled into a unit such as an inverter unit. For example, as shown in FIG. 8, when the device 1 is located between a pair of cooling plates 9, two heat conducting sheets 10 made of insulating material are inserted between the plates 9 and the outer surfaces of the heat sinks 2, 3.
Moreover, a coating resin such as polyamide resin is applied to the surface of the heat sinks 2, 3 prior to the molding to create a desired adhesion between the heat sinks 2, 3 and the mold resin 7. However, in the semiconductor device 1, the distance between the heat sinks 2, 3 is in the range between 1 and 2 mm, so it is difficult to apply the coating resin on the inner surfaces of the heat sinks 2, 3. It is also difficult to inspect the coating quality.